A cell terminal, disclosed in Japanese Patent Laying-Open No. 2001-6746 (Patent Document 1), for example, in which a plurality of members made of different metallic materials are bonded to each other is known in general.
In the aforementioned Patent Document 1, there is disclosed a lithium ion cell including a cell can made of Al functioning as a positive electrode, a clad body (positive-electrode terminal) whose one surface side is welded to this cell can and whose another surface side is welded to a lead (cell terminal connecting plate) made of Ni, and a negative-electrode terminal connected to a negative electrode in a state insulated from the cell can. An Al layer and an Ni layer are bonded to each other in the clad body of this lithium ion cell, and the Al layer (first metal layer) is positioned on the cell can side, while the Ni layer (second metal layer) is positioned on the lead side. Thus, the lithium ion cell has a weld structure of the lead made of Ni larger in electric resistance than Al and the Ni layer of the clad body, whereby welding between the lead and the clad body becomes easy due to resistance welding. Although not clearly described in Patent Document 1, the clad body is conceivably in a state (overlay (OVERLAYS) shape) where the Al layer and the Ni layer are bonded to each other over the whole surfaces.